Magnesium base alloy



Patented Mar. 22, 1932 UNITED STATES PATENT orrlca 393E353 T. WOOD, 01LAKEWOOD, AND HAROLD H. BLOCK, OF CLEVELAND, OHIO, AS- SIGNORS TOAMERICAN MAGNESIUM CORPORATION, OF PITTSBURGH, PENNSYL- 'mennsrun BASEAnnoy its Drawing.

This invention relates to magnesium base alloys and is directed to thedevelopment of alloys of this class characterized by a high resistanceto corrosion.

The specific gravity of magnesium is only abouttwo thirds of that ofaluminum and this constitutes a decided advantage in favor of mangnesiumand its alloys. For this reason efiortsare constantly being exerted toimprove-magnesium base alloys in those respects in which aluminum basealloys now have the advantage, for instance, corrosion resistance. Whilemany articles made from magnesium base alloys are now in daily service,vit is desirable that alloys be produced which will be able tosatisfactorily resist conditions more severe than usual, for instanceconstant exposure to salt-air or aggravated atmospheric conditions,without danger of failure from corrosion.

The principal object of the'invention is the productionof magnesium basealloys of higher, corrosion resistance than characterizes the usefulmagnesium base casting allows which have heretofore been available.

An important object of the invention is to provide magnesium base alloysof high corrosion resistance with physical properties adequate tofulfill commercial needs. The terms magnesium base alloys and mag,-

-nesium alloys as used in this specification and the appended claims areto be understood as meaning alloys containing more than 50 per cent ofmagnesium.

The magnesium-aluminum-manganese alloy widely used commercially in thiscountry for casting purposes exhibits physical properties which arecomparatively excellent and are amenable to improvement by sultv ableheat treatments. Its combination of properties has been the bestheretofore 0b-' tainable in a general purpose castmgalloy, but undersevere conditions it is noticeably subject to corrosion. Variousprotective coatings more or less beneficial have been devised andapplied to the alloy to improve its corrosion resistance. Protectivecoatings, however, only attempt to counteract an innate evil whereas thealloys which form the subject of our present invention are in-Application riled August 6,

1931. Serial No. 555,532..

herently resistant to corrosion and exhibit that important property to amarked extent even without protective coatings of any sort.

In the course of our investigations, wherein alloys were compounded ofvarious constituents and tested for physical properties and corrosionresistance We found that magnesium alloys containing varying amounts oftin, zinc and cadmium with or without other constituents arecharacterized by satisfactory physical properties and corrosionresistance. The alloys may contain from 0.1 per cent to 15.0 per centtin, from 0.1 per cent to 5.0 per cent zinc, and from 0.1 per cent to20.0 per cent cadmium. The amounts of these constituents may vary widelybut when all are present their cooperative efiect is high desirable. Ourexperience also indicates that whereas aluminum as an alloy base ishighly resistant to corrosion, its presence in a magnesium base alloydoes not, in general, improve the property mentioned and in some casesmav even increase the susceptibility of the alloy to corrosion.

In testing our new alloys we have subjected the same to particularlyaggravated corrosive conditions.

One such test which has been standardized for the purpose of comparingdiflerent alloys consists in repeatedly immersing the alloy in a 3 percent aqueous solution of sodium chloride alternating with exposures tothe atmosphere. This test is chosen not only because it is more severethan ordinary service conditions but also for the reason that it givesnumerically measurable corrosion effects in a fairly short time. In thistest a duration of 40 hours has been adopted as adard.

n ln carrying out the test a number of tensile manganese casting alloy,mentioned above, at

the end of 40 hours of test, had lost between per cent and per cent ofits original strength. On the other hand, a magnesium base alloycontaining tin 2.03 per cent, zinc 2.20 per cent, and cadmium 2.23 percent,lost under the same conditions only 15 per cent of itsoriginal'strength. At the start the two alloys had a tensile strength of25,000" and 22,800 pounds per square inch, respectively, and at theclose of the test the tensile strengths were 12,000 and 18,380 poundsper square inch. Our allo therefore, at the start'of the test was somewat inferior in strength but at the end showed about 50 per centimprovement over the prior alloy. Further improvement in our alloy waseffected by heat treatment, the heat treated specimen losing about 11 ercent-of its original strength.

e have also found that the presence of one or more of the elements lead,manganese and mercury effects a further improvement. The lead may beintroduced in amounts from 0.1 percent to 10.0 per cent, the manganesefrom 0.1 per cent to 5.0 per cent, and the mercury to a lesser extent inthe neighborhood of about 0.1 per cent to 0.5 per cent. Althoughmanganese when added in amounts from 0.1 to 5.0 per cent givesbeneficial results, the preferred results are obtained when the alloycontains not less than about 0.5 per cent.

For example, a magnesium alloy containing tin 3.1 per cent, zinc 3.3 percent, cadmium 3.3 percent, and lead 3.2 per cent, subjected to the abovetest, showed a loss of 13 per cent of ori al tensile. strength, whichwas 24,000 poun s per square inch in the as cast condition. After heattreatment the loss was only 7.5 per cent of the original strength.

As an example of the beneficial effect of lead and manganese, amagnesium alloy containing tin 2.11 per cent, zinc 2.3 per cent,

cadmium 2.00 er cent, lead 2.07 per cent, and

manganese 1. 4 per cent, with a tensile strength of 24,200 pounds persquare inch as cast, and 27,700 ounds after heat treatment, showed aloss 0 12 per cent of its original strength in the as-cast condition andinthe heat treated condition only 9.5 per cent.

As an example of the beneficial effect of the addition ofmanganesealone, a magnesium alloy containing tin 5.0 per cent, zinc 2.0 per cent,cadmium 2.0 r cent, and manganese 1.0 per cent, lost onll0 per cent ofits original strength as cast. 1

As an example of the beneficial effect of the addition of lead andmercury, a magnesium alloy containing tin 2.00 per cent, zinc 2.00 percent, cadmium 1.59 per cent, lead 1.59 per cent, and mercury 0.20 percent, with an as-cast strength of 24,300 pounds per square inch, showeda loss of only 7 per cent of its original strength.

As the result of numerous tests on mag- Tin 6 per cent Cadmium 1 percent Zinc 1 per cent Manganese 1 per cent Magnesium balance As a resultof a large number of tests we have determined that the advantageouseffects of the alloying elements herein disclosed and claimed areobservable over a wide range of composition in the case of each.element.

The corrosion test used in each case was the same as that heretoforedescribed, in which the prior magnesium-aluminum-manganese casting alloyhitherto found most advantageous suffered a loss in. strength of from 50to 60 per cent. The following are the results of some of these tests:

A sand cast magnesium base alloy containing 2 per cent cadimum, 2.0 percent lead 2.0 per cent zinc, and 15.0 per cent tin showe a loss of only6.0 per cent of its original strength after the corrosion test.

A sand cast magnesium base alloy containing 2.0 per cent cadmium, 2.0per cent lead, 2.0 per cent tin, and 5.0 per cent zinc showed a loss instrength of only 7.0 per cent.

A sand cast magnesium base alloy containing 20.0 per cent cadmium, 2.0per cent lead,

2.0 per cent tin, and 2.0 per cent zinc showed a loss in strength ofonly 5.0 per cent.

' A sand cast magnesium base alloy containing 2.0 per cent cadmium, 10.0'per cent lead, 2.0 per cent tin, and 2.0 per cent iinc showed a lossin strength of only 9.0 er cent.

A sand cast magnesium base a oy containing 2.0 per cent cadmium, 3.6 percent manganese, 2.0 per cent lead, 2.0 per cent tin and 2.0 per centzinc showed a loss in strength of only 4.0 per cent.

In compounding the alloy, the various constituents may be added bymethods well known to the art, such as by the addition in the ure stateto the moltenma by t e use of so-called rich alloys or hardeners of twoor more of the alloying ele-' ments. We do not wish to stipulate a. settechnique since practice usual varies with the equipment and personnelof t foun ries.

Our alloys are especiall useful for casting purposes, and may be sujected, in the cast.

be different esium or in partof our earlier application Serial No.504,430, filed December 23, 1930.

What we claim is- 1. A magnesium base alloy containing 0.1 per cent to15.0 per cent tin, 0.1 per cent to 5.0 per cent zinc, and 0.1 per centto 20.0 per cent cadmium.

2. A magnesium base alloy containing 0.1

. per cent to 15.0 per cent tin, 0.1 per cent to 5.0 per cent zinc, 0.1percent to 20.0 per cent fadamium, and 0.1 per cent to 10.0 per cent 3.A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin, 0.1per cent to 5.0 per cent zinc, 0.1 per cent to 20.0 per cent cadmium,and 0.5 per cent to 5.0 per cent manganese.

4:. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin0.1 per cent to 5.0 per cent zinc, 0.1 per cent to 20.0 per centcadmium, and 0.1 per cent to 0.5 per cent mercury.

5. A magnesium base allow containing 0.1 per cent to 15.0 per cent tin,0.1 per cent to 5.0 per cent'zinc, 0.1 per cent to 20.0 per centcadmium, 0.1 per cent to 10.0 per cent lead, and 0.5 per cent to 5.0 percent manganese.

' 6. A magnesium base alloy containing 0.1 per cent to 15.0 per centtin, 0.1 per cent to 5.0 per cent zinc, 0.1 per cent to 20.0 per centcadmium, 0.1 per cent to 10.0 per cent lead,

and 0.1 per cent to 0.5 per cent mercury.

7. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin,0.1 per cent to 5.0 per cent zinc, 0.1 per cent to 20.0 per centcadmium, 0.1 per cent to 10.0 percent lead, 0.5 per cent to 5.0 per centmanganese, and 0.1 per cent to 0.5 per cent mercury.

8. A magnesium base alloy containing 0.1 per cent to 15.0 per cent tin,0.1 per cent to 5.0 per cent zinc, 0.1 per cent to 20.0 per centcadmium, 0.5 per cent to 5.0 per cent manganese, and 0.1 per cent to 0.5per cent mercury.

9. A magnesium base alloy containing about 6 per cent tin, about 1.0 percent manganese, about 1.0 per cent zinc, and about 1.0 per cent cadmium.v

10. A magnesium base alloy containing 0.1 per cent to 15.0 percent ti'n,0.1 per cent to 5.0 per cent zinc, 0.1 per cent to 20.0 per centcadmium, 0.1 per cent to 10.0 per cent lead A 0.1 per cent to 5.0 percent manganese, an 0.1 per cent to 0.5 per cent mercury.

11. A magnesium base alloy containing 0.1- per cent to 15.0 per centtin, 0.1 per cent to 5.0 per cent zinc, 0.1 per cent to 20.0 per centcadmium, 0.1 per cent to 5.0 per cent manganese, and 0.1 per cent to 0.5percent mercury.

In testimony whereof we hereto aflix our signatures.

A Y ROBERT T. WOOD.

HAROLD, H: BLOCK.

